A check valves is a passive valve that is opened when subject to a flow in a first direction and closed when subject to a flow in a second direction, most commonly the first and second directions are opposite. Check valves can be used to control the flow of any kind of fluid, gaseous or liquid, or a fluid containing solid particles such as slurry.
Previously known check valves comprises a diaphragm adapted to seal against a valve seat when a pressure is exerted on the diaphragm. The diaphragm is usually mounted to a valve housing either with a centrally places fixation device or using a movable joint fixated to a peripheral portion of the diaphragm. Embodiments in which the diaphragm is fixated with a centrally placed fixation device has disadvantages in that the centrally placed fixation device needs to be attached to the valve housing, and therefore some kind of attachment are usually blocking the flow. Furthermore, centrally fixated diaphragms needs to perform a funnel deformation, which requires a greater force than a linear deformation, and the valve never opens fully even if the diaphragm is deformed into a steep funnel, i.e. a funnel having a small angle between the center axis of the funnel and the funnel wall. Embodiments in which the diaphragm is fixated to a peripheral portion has the disadvantage that they require a large space to open fully since the entire diaphragm needs to be positioned in the direction of the flow, furthermore this 90° opening places large strain on the joint, especially if the joint functions by means of resilient material.